In psychology and cognitive science, a memory bias is a cognitive bias that either enhances or impairs the recall of a memory (either the chances that the memory will be recalled at all, or the amount of time it takes for it to be recalled, or both), or that alters the content of a reported memory. There are many types of memory bias, including:

Beneffectance: perceiving oneself as responsible for desirable outcomes but not responsible for undesirable ones. (Term coined by Greenwald, 1980)

Context effect: that cognition and memory are dependent on context, such that out-of-context memories are more difficult to retrieve than in-context memories (e.g., recall time and accuracy for a work-related memory will be lower at home, and vice versa).

Cryptomnesia: a form of misattribution where a memory is mistaken for imagination, because there is no subjective experience of it being a memory.

Egocentric bias: recalling the past in a self-serving manner, e.g. remembering one's exam grades as being better than they were, or remembering a caught fish as being bigger than it really was

Hindsight bias: the inclination to see past events as being predictable; also called the "I-knew-it-all-along" effect.

Humor effect: that humorous items are more easily remembered than non-humorous ones, which might be explained by the distinctiveness of humor, the increased cognitive processing time to understand the humor, or the emotional arousal caused by the humor.

Leveling and Sharpening: memory distortions introduced by the loss of details in a recollection over time, often concurrent with sharpening or selective recollection of certain details that take on exaggerated significance in relation to the details or aspects of the experience lost through leveling. Both biases may be reinforced over time, and by repeated recollection or re-telling of a memory. (e.g., Koriat,­ Goldsmith and ­Pansky, 2000)

Levels-of-processing effect: that different methods of encoding information into memory have different levels of effectiveness (Craik & Lockhart, 1972).

Misattribution: when information is retained in memory but the source of the memory is forgotten. One of Schacter's (1999) Seven Sins of Memory, Misattribution was divided into Source Confusion, Cryptomnesia and False Recall/False Recognition

Modality effect: that memory recall is higher for the last items of a list when the list items were received via speech than when they were received via writing.

Suffix effect: the weakening of the recency effect in the case that an item is appended to the list that the subject is not required to recall (Morton, Crowder & Prussin, 1972).

Suggestibility: a form of misattribution where ideas suggested by a questioner are mistaken for memory.

Telescoping effect: the tendency to displace recent events backward in time and remote events forward in time, so that recent events appear to be more remote, and remote events, more recent.

Testing effect: that frequent testing of material that has been committed to memory improves memory recall.

Tip of the Tongue phenomenon: when a subject is able to recall parts of an item, or related information, but is frustratingly unable to recall the whole item. This is thought to be an instance of "blocking" where multiple similar memories are being recalled and interfere with each other (Schacter, 1999)

Verbatim effect: that the "gist" of what someone has said is better remembered than the verbatim wording (Poppenk, Walia, Joanisse, Danckert, & Köhler, 2006).

Von Restorff effect: that an item that sticks out is more likely to be remembered than other items (von Restorff, 1933).

Zeigarnik effect: that uncompleted or interrupted tasks are remembered better than completed ones.